Polypyyrole based core-shell structured composite based humidity Sensor operable at room temperature

The present work explores the humidity sensing performance of core-shell structured Polypyrrole/Tantalum pentoxide (PTO) composite. For the study, Polypyrrole (PPy) prepared by chemical oxidative polymerization was mixed mechanically with different mass ratios of Tantalum pentoxide (Ta2O5) to form four PTO composites. The compositional properties of PTO composites were studied by FTIR and XRD techniques. The SEM and TEM morphological studies revealed core-shell structures of the composites. For the sensing studies, the film of PPy and each of PTO composites were prepared by implanting each sample on a glass plate using simple spin coating technique. Of all the samples prepared, the PTO-4 composite, as an epitome of near perfect sensing, has shown humidity sensing response of 99.99% and has recorded a good response and recovery times of 6 s and of 7 s respectively. It has also recorded a good real sensitivity, limit of detection (LOD), linearity, hysteresis and has shown good sensing stability over a period of two months. As compared to PPy, the porosity, water content and degree of swelling of PTO-4 composite has remarkably enhanced. The humidity sensing mechanism of the composite has been discussed as due to the formation of chemisorption and physisorption layers followed by capillary condensation process.